The present invention relates to a method for simulating “malfunctioning” solenoid valves for an internal combustion engine by influencing the activation and/or deactivation times of the solenoid valve, wherein the solenoid valve is powered/energized with current of a predetermined, variable current strength for realizing opening and closing processes, wherein the closing or opening process is forced after activating the current feed to the solenoid valve at the activation point in time, and the opening or closing process is forced after deactivating the current feed to the solenoid valve at the deactivation point in time.
A “malfunctioning” solenoid valve is understood to be a solenoid valve that opens too early and/or too late and/or that closes too early and/or too late. For the case that the solenoid valve closes or opens too early and/or too late, this means that the solenoid valve is activated at an advanced and/or retarded point in time. An advanced/retarded activation thus defines a shortened/lengthened activation time. For the case that the solenoid valve opens or closes too early and/or too late, this means that the solenoid valve is deactivated at an advanced and/or retarded point in time. This means that the deactivation time is shortened or lengthened in this case.
The demonstration of failure effects and fault detection for certifying a vehicle diagnostics system, especially for CARB (California Air Resources Board) certification/release is necessary to be able to show that the system can detect defective components that might possibly influence emissions before these emissions reach a critical value. For this purpose, modified, “malfunctioning” solenoid valves, manufactured as extra components, are currently used.
This has the disadvantage that this procedure causes high costs and high complexity in production. In addition, the development times for such intentionally malfunctioning modifications of solenoid valve are very long and the distribution or transport of modified solenoid valves between the individual development locations is logistically very complex. In addition, the modified solenoid valves can be affected by wear and other problems and their properties can change due to use or long storage times. The limits up to which the system to be calibrated detects faults are based on the modified solenoid valves, wherein the control software is limited in its “capability.” In particular, defects that involve a shifting of the switching times of the solenoid valves should be detected.
Switching valves and methods for controlling solenoid or switching valves are known from, among other publications, DE 10 2012 213 399 A1. That document describes a method for regulating a switching process of electromagnetically actuated switching valves for the exact control of valves under consideration of temperature oscillations and other interference sources. In addition, in the not yet published DE 10 2014 202 428.5, an electrohydraulic switching valve and a method for low-noise control of such a switching valve are described.
A conventional solenoid valve is formed essentially from a poppet that is arranged immovable in the axial and radial directions relative to a slide. In addition, it includes a magnetic armature, a primary coil that is connected to an electrical connection, and an upper spring and a lower spring that cause, among other things, the movement of the slide and poppet.
Here, the solenoid valve is held closed due to the higher spring force in the lower or dominant spring in comparison to the upper or non-dominant spring. By feeding a sufficient current into the coil, the sum of the forces from the non-dominant spring force and the magnetic force generated by the current flowing through the primary coil becomes greater than the spring force of the dominant spring, whereby the slide and the poppet are moved and the solenoid valve is closed or opened. If the current is cut or the current strength is reduced so much that the spring force of the dominant spring becomes greater than the sum of the spring force of the non-dominant spring and the magnetic force, the slide and poppet move and the solenoid valve is opened or closed again.
There is also the possibility that the solenoid valves are formed with the reverse function, that is, the solenoid valve is held closed or open by the dominant spring, the valve is opened or closed by the current feed, and it is closed or opened again by cutting the current, whereby the variations explained below can also be realized in the opposite sense.